Laser textured magnetic disk

ABSTRACT

A magnetic disk is provided which comprises a nonmetallic glass or glass ceramic substrate having one or more under layers, a magnetic layer applied over the under layers, and a hard carbon layer applied over the magnetic layer. A plurality of bumps are formed on the magnetic disk by applying a beam from a near infrared wavelength laser to the surface of the carbon layer.

FIELD OF THE INVENTION

[0001] The present invention pertains to the texturing of magneticdisks. More particularly this invention pertains to using a nearinfrared wavelength laser to create bumps on a nonmetallic substratebased magnetic disk.

BACKGROUND OF THE INVENTION

[0002] A direct access storage device uses magnetic disks to storeelectronic data. The disks are rotated on a central axis in combinationwith magnetic heads for reading and writing magnetic signals.

[0003] A “contact start/stop” (CSS) system uses a magnetic head which isin contact with the magnetic disk surface only when the disk isstationary. When the disk starts to rotate the magnetic head slides offthe surface eventually flying fully lifted from the disk surface.

[0004] A smooth recording surface is preferred to permit the magnetichead to ride as close as possible to the disk surface. In order to avoidstiction, which occurs during the start process in a CSS system, atextured region of the rotating disk surface is used for the contactarea with the magnetic head. The surface texture in a contact start/stopregion reduces the contact stiction and friction. The magnetic head ismoved to the contact region at the appropriate times by the drivecontroller.

[0005] It is known in the art to use a laser to create bumps on thesurface of the disk to produce a textured region as a contact area in aCSS disk drive system. Laser zone texturing (LZT) processes are widelyused in the hard disk drive industry to allow precise control of theroughness of the hard disk contact area. In laser zone texturing, anannular area typically 2-3 mm wide of the disk surface is roughened by alaser. The laser produces micro-sized bumps to provide a take off andlanding zone for the flying head during the contact start/stopoperation. Usually, the laser texturing process is applied to anonmagnetic substrate prior to conventionally employed processes forproducing the magnetic recording disks.

[0006] Traditionally, a magnetic disk is manufactured by initiallystarting with an aluminum magnesium (AlMg) substrate which is thenplated with nickel phosphorus (NiP). The texturing is then performed onthe plated NiP layer. On top of the NiP plated AlMg substrate, amagnetic layer is sputter deposited.

[0007] In particular, because of their performance characteristics, itis desirable to use a tightly focused laser beam, with TEM00 spatialmode and Gaussian intensity distribution profile, from diode pumpedneodymium-doped yttrium-lithium-fluoride (Nd:YLF) or a neodymium-dopedyttrium-vanadate (Nd:YVO4) solid state laser to create the bumps on adisk surface. The Nd:YVO4 laser is also referred to as an Nd:Vanadatelaser or a Vanadate laser. These lasers are in the near infrared(near-IR) family of lasers. The near-IR wavelength lasers providesufficient absorption and coupling of laser energy into the smoothamorphous NiP material that had been deposited onto the AlMg substrate.

[0008] An example of a laser texturing tool is provided in commonlyowned U.S. Pat. No. 6,013,336, Baumgart et al, “Procedure Employing aDiode Pumped Laser for Controllably Texturing a Disk Surface”. Otherlaser texturing tools are well known to those skilled in the art.

[0009] In the last few years the use of alternative nonmetallicsubstrates such as glass or glass-ceramic substrates has become widelyaccepted in the industry due to the superior mechanical advantages ofglass and glass-ceramic material. A glass based substrate provides asmoother surface for the magnetic layer. The smoother the recordingsurface, the closer the proximity of the head to the disk. This allowsmore consistent and predictable behavior of the air bearing support forthe head which enables a higher recording density.

[0010] However, since glass materials are optically transparent in thenear IR wavelength range, the vanadate laser based texturing toolscannot be used for the laser zone texturing process on the raw glasssubstrate.

[0011] As an alternative laser texturing process, a CO₂ laser basedsystem is known in the industry to be used for zone texturing raw glasssubstrates. This is because the glass substrate material is sufficientlyabsorbent at wavelengths produced by CO₂ lasers. The textured glasssubstrate can then be processed to the finished magnetic disk bydepositing at least one underlayer, then a magnetic layer and then aprotective overcoat (commonly a carbon or carbon-based layer). Examplesof a laser texturing tool for glass substrates is found in commonlyowned U.S. Pat. No. 6,107,599, Baumgart et al, “Method and Tool forLaser Texturing of Glass Substrates”.

[0012] However, the bump formation mechanism as well as the bump shapefor the above processes are different. Bump formation on a NiP-platedAlMg disks is governed by rapid melting and resolidification process ofthe heated spot on the substrate surface, and the final bump shapedepends on thermocapillary and chemicapillary effects created by thelaser pulse. While the bump formation on a glass disks (using CO₂ laser)is due to laser absorption in the glass and the consequent thermalexpansion of the heated area.

[0013] While the CO₂ laser can be used to texture raw glass substrates,there are limitations in the ability of CO₂ laser texturing tools tooptimally texture disks. Therefore, it is desirable to provide a methodfor texturing the glass based substrate disks using the Nd:Vanadatelaser because Nd:Vanadate lasers provides greater flexibility in theprocess of producing a textured zone.

[0014] Furthermore, the Nd:Vanadate laser texturing systems arecurrently widely used in the manufacturing texturing process ofNiP-plated AlMg substrates. It is more economical to be able to use themore readily available laser systems for the glass substrate disks.

[0015] An approach to providing zone texturing of a glass substrate hasbeen demonstrated in U.S. Pat. No. 5,980,997. In this approach, a smoothmetallic layer is first deposited on a glass substrate, and the metalliclayer is then textured by a laser beam. The metallic layer is preferablyimpact resistant, hard and has a high-melting temperature greater than1000 degrees centigrade. Since such a deposited metallic layer (i.e.,texture layer) absorbs laser energy at near-IR wavelengths, a Vanadatelaser based texturing tool can be used to produce a textured zone on theglass substrate deposited with a texture layer. The textured glasssubstrate then undergoes the conventional processes for themanufacturing of a magnetic disk. A disadvantage of this approach isthat an extra step is added to the manufacturing process of depositing atexture layer before the laser texturing process is completed. Such astep obviously adds to the manufacturing costs of a magnetic diskproduction. Therefore, there is a need for a laser texturing process forglass-substrate magnetic disks which does not add to any of theproduction costs and allows for greater flexibility in the use of theVanadate-laser-based texturing tool.

[0016] It is also desirable to provide a process for marking a disk,including alphanumeric writing, on a sputtered or finished disk. Diskmarking can be used to distinguish a good and a defective side of asingle sided finished disk by producing a textured ring or otherarbitrary pattern on the defective side of the finished glass disk. Sucha marked finished glass disk can be used in a load/unload drive and notnecessarily in a contact start/stop drive. Implementation of suchmarking process in manufacturing can extend applicability of theexisting texturing systems to disk marking processes.

[0017] The marking of a disk can also be useful for identifying a disk.When a disk is in use, installed in a computer system, it is helpful tobe able to determine when and where the disk was manufactured. Marking adisk with this information enhances quality assurance processes.

[0018] It is also desirable to use textured glass substrate disks todetermine the glide height of a magnetic head over a magnetic disk. Itis currently known in the industry to use textured disks to test whethera magnetic head flying over a disk touches the disk surface which causesproblems.

[0019] During reading and recording operations, the head is positionedas close to the disk surface as possible. There are topologicalasperities, typically, only a few microns (or smaller) in diameter andheight range from about a few micro-inches to sub-micro inches, formedon the surface of a disk which make it necessary to limit the proximityof the head to the disk surface. Conventional disk drives aremanufactured with precise specifications including maximum glide heightfor a magnetic head above the data zone. In recognition of theinevitable topographical asperities, conventional practice comprisestesting each magnetic disk to determine if the maximum glide heightrequirement is met. Such testing typically comprises the use of a deviceknown as a glide tester.

[0020] Conventional glide testers typically use a reference diskcontaining a single (or multiple) protusions formed by photolythographictechniques, or single (or multiple) laser-textured bump(s) on AlMgsubstrates, or raw glass substrates, having a defined height. Thereferenced disk is rotated and a magnetic head is lowered until themagnetic head contacts the bump at which point an electrical signal isgenerated indicating the glide height. Of particular significance is theneed for the bumps on the reference disk to accurately simulateasperities inevitably present on the surface of a magnetic disk. Thereexists a need for an efficient and cost-effective method to produce sucha reference disk.

[0021] There is also a need to better control the shape and orientationof laser produced bumps to provide a more controllable contactstart/stop zone wherein stiction is reduced without compromisingdurability. It is also desirable to control and adjust the bump shapefor a glide tester reference disk to optimize electrical signalgeneration during the process of glide height calibration, and toovercome signal generation issues associated with CO2 laser producedbumps on raw glass substrates. More particularly, it is desirable toefficiently produce bumps with elongated shapes to achieve these goals.

[0022] One or more of the foregoing problems are solved and one or moreof the foregoing needs are met by the present invention.

SUMMARY OF THE INVENTION

[0023] A magnetic disk is provided which comprises a glass orglass/ceramic substrate, one or more under layers, a magnetic layerapplied over the substrate, and a carbon layer applied over the magneticlayer. A plurality of bumps are formed on the magnetic disk by applyinga laser beam to the surface of the carbon layer.

[0024] In a further embodiment of the present invention a method isprovided for preparing a magnetic disk comprising first applying one ormore under layer(s) and a magnetic layer to a glass or glass ceramicsubstrate. A carbon overcoat layer is then applied over the magneticlayer. A plurality of bumps are incorporated onto the surface of thedisk by applying a laser to the surface of the carbon layer. In afurther embodiment a lubricant is applied over the carbon overcoatlayer.

[0025] In a further embodiment of the present invention the bumpformation process can be conducted after applying the lubricant layer onthe magnetically sputtered disk.

[0026] In a further embodiment, a plurality of bumps formed in aconcentric circle using the laser provides a contact start/stop zone forthe magnetic disk.

[0027] In a further embodiment, a single or a plurality of bumps providea means for calibrating glide height of a transducer head flying overthe magnetic disk.

[0028] In a further embodiment, a plurality of bumps provide a means formarking the magnetic disk.

[0029] In a further embodiment, a cylindrical lens system is used toform elliptical or elongated bumps on the surface of the finished glasssubstrate magnetic disk.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 illustrates a cross-section of a glass substrate basedmagnetic disk containing a bump.

[0031]FIG. 2 illustrates a magnetic disk containing landing and datazones and showing a block diagram of a laser creating the bumps for thelanding zone.

[0032]FIG. 3 is a graph showing the bump height variation versus thelaser power on a finished glass disk.

[0033]FIGS. 4a-d are illustrations of the bumps created by variouspowers of the Nd:Vanadate laser on the finished glass disk.

[0034]FIG. 5 is an illustration of a one sided glass disk marked with aring.

[0035]FIG. 6 illustrates a glide height test disk.

[0036]FIG. 7 illustrates a cylindrical lens system that converts acircular beam into elliptical shape.

[0037]FIG. 8 illustrates elongated bumps on the surface of the finishedglass disk.

[0038]FIG. 9 illustrates a three dimensional view of the central portionof an elongated bump of FIG. 8.

[0039]FIG. 10 illustrates the profile of the elongated bump along theshort axis A of FIG. 9.

[0040]FIG. 11 illustrates the profile of the elongated bump along thecentral portion of the long axis B of FIG. 9.

[0041]FIG. 12 illustrates a graph of bump height variation versus laserpower for elongated bumps.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0042] The present invention applies a near IR wavelength laser zonetexturing tool for use on a nonmetallic substrate, such as a glass orceramic-glass, finished magnetic disk. While the preferred embodiment isdescribed herein with reference to a glass substrate, it is understoodby those skilled in the art, that the invention described herein mayalso be implemented using ceramic glass substrates and other nonmetallicsubstances known to be used in the manufacturing of magnetic disks fordata storage. Therefore, throughout this description of the invention,the reference to “glass” is used to generally refer to glass and ceramicglass substrates, as well as other nonmetallic substrates.

[0043] The magnetic disk is conventionally produced by sputterdepositing one or more underlayer(s), a magnetic layer and a protectivecarbon overcoat layer. After all the layers have been added a near IRwavelength laser beam such as a vanadate laser system is used to providetexturing. The process may also be applied to a magnetically sputteredglass substrate based disk after it has been lubed in accordance withthe normal lube process for magnetic disks.

[0044] Referencing FIG. 1, a cross section of a magnetic glass substratedisk 10 is shown. According to standard industry practices, a series ofunder layers of metal alloys are sputter applied, according toconventional techniques, prior to the application of the actual magneticlayer which holds the electronic data. These under layers are used toimprove the magnetic performance quality of the recording substrate. Thefirst under layer 14 is preferably nickel aluminum (NiAl) which is thefirst substance sputtered onto the glass substrate 12. This layer issometimes referred to as a seed layer. The next under layer that isapplied is the chromium vanadium (CrV) 18 which is followed by a layerof cobalt chromium (CoCr) 20. After these under layers have beenapplied, a magnetic layer of cobalt chromium platinum boron (CoCrPlBo)22 is applied. After the magnetic layer is sputtered onto the disk, acarbon overcoat (coc) layer 24 is applied. The carbon overcoat materialcomprises a carbon which has been nitrogenated or hydrogenated in orderto produce a protective, diamond-like substance. After the sputterprocesses are completed, the magnetic disk goes through a lubricationprocess to complete the production process of the magnetic disk byadding a layer of lubricant 26. In the preferred embodiment, a commonlubricant that is used in the industry is the commercially availableZ-dol 4000 lubricant. Other lubricants may also be used. A lubricateddisk is referred to as a “finished disk”.

[0045] In the preferred embodiment, the seed layer is a nickel aluminumalloy. However, other conventionally employed metal alloy underlayersubstances known to be used in the production of magnetic disks may alsobe used in accordance with the present invention. Likewise, in thepreferred embodiment the under layers and magnetic layer of the presentinvention comprises cobalt based alloys with the carbon overcoatprotection. Other under layers, magnetic layers and hard protectiveovercoat layers may also be used.

[0046] The thicknesses of the under layer, magnetic layer, and carbonovercoat layer are consistent with conventional practices in themanufacturing of a magnetic disk media. In the preferred embodiment, thenickel aluminum is approximately 300 angstroms, the CrV is approximately300 angstroms, the CoCr is approximately 40 angstroms and the CoCrPlBois approximately 200 angstroms. The carbon overcoat layer is applied ata thickness of approximately 50 angstroms.

[0047] Referencing FIG. 2, in accordance with the present invention, thesurface of the finished glass or glass/ceramic substrate based magneticdisk 30 is provided with a textured takeoff and landing (contactstart/stop) zone by utilizing a pulse focused laser beam 34 provided bya near IR wavelength laser such as an Nd:Vanadate laser 36. The beam 34is directed onto the locations of the disk surface 30 by passing thebeam 34 through a focusing lens 37.

[0048] The resulting laser texture comprises a plurality of accuratelypositioned protrusions or bumps 39 with controlled height and geometryto optimize tribologic and magnetic requirements compatible with therequirements of a high density storage landing zone 38. The bumps 39 inthe landing zone 38 are spaced according to the tribology performancerequirements or can be spaced randomly. The disk 30 has an outerdiameter 40 and an inner diameter 42. The width of the landing zone 38is typically about 2-3 mm. The landing zone 38 is preferably spaced 3½-5or 6 mm from the disk inner diameter. The remaining surface area of thedisk is referred to as the data zone 41.

[0049] The preferred near IR wavelength laser used is an Nd:Vanadate(Nd:YVO4) laser system. In an Nd:Vanadate laser, a neodymium-dopedyttrium-lithium-vanadate crystal 43 is used as the lasing medium toproduce the laser stream. Other near IR wavelength lasers, such asNd:YLF laser, may also be used. An example of a commercially availablevanadate laser is the T-Series Laser System available fromSpectra-Physics.

[0050] One of the critical optical parameters in a laser texturingprocess for achieving tight control on the bump height is the depth offocus of the laser spot on the disk surface. A laser texturing toolsystem with a longer depth of focus is less sensitive to disk-to-diskthickness variations and more forgiving of minor imperfections in theoptical and mechanical alignment in the system. A longer depth of focushas the advantage of providing a tighter control on the average bumpheight during manufacturing production. In order to achieve the samebump diameter, the depth of focus for an Nd:Vanadate laser texturingsystem is a few times longer than the depth of focus for the CO₂ laserbased system. This provides greater consistency in the textured zonesbetween disks and provides a more economical way of producing the bumps.

[0051] The Nd:Vanadate laser pulse width used in texturing process, istypically a few times shorter than the CO₂ laser pulse width. Thereforethe Nd:Vanadate laser has less thermal diffusion in the glass substrateand therefore has the ability to form smaller bumps. The Nd:Vanadatelaser pulse energy is mostly absorbed by the sputtered film which isconsistently opaque to the vanadate laser beam. This process also takesadvantage of the better disk to disk compositional and structuralconsistency of the sputtered magnetic layers (film) on the glass/glassceramic substrate.

[0052] The shape of the bumps formed on a sputtered or finished disk,for a fixed laser spot size and pulse duration, is mainly dependent onthe pulse energy that is applied. The bumps created on a sputtered diskcan be dome-shaped (similar to those formed by a CO₂ based laser on araw glass substrate), or quasi-dome shape, or sombrero-shaped, or evenhave a V-shape crater in the center of the bump if the laser pulseenergy is increased. The laser pulse energy can also cause cracking orbreakage in the sputtered layer resulting in other mostly irregular bumpshapes.

[0053] The bump height range of interest for a contact start/stop zone,the 10-30 nanometer range (or lower), does not require high laser pulseenergy that can damage, or burn through, the sputtered layers.

[0054]FIG. 3 illustrates a graph of the bump height variation 45relative to various laser powers 46 (the power curve 47). The bumpheight range of practical interest on a sample production disk isbetween 10 and 25 nanometers. The graph depicts the power curve fortested disks having the disclosed sputtered layer structure. The laserpower used to produce the desired bump height is dependent on the laserbeam spot diameter, pulse duration and pulse energy. As shown, the slopeof the curve is not the same at different segments of the curve. Thisrelates to the fact that the increase in laser power not only increasesthe bump height, it also induces changes in the bump slope and shape.

[0055]FIGS. 4a-4 e illustrates the variations in the bumps produced bythe various laser powers. FIG. 4a illustrates a dome-shaped bumpproduced by 49.9 micro watts of power. FIG. 4b shows a semi dome shapedbump produced by 57.5 micro watts of power. The bump diameter isslightly larger than the dome-shaped bump. FIG. 4c shows asombrero-shaped bump produced by 67 micro watts of power and FIG. 4dillustrates a crater-shaped bump produced by 72.6 micro watts of power.

[0056] The foregoing process may also be implemented for disk marking.The disk marking process can be used to produce, but is not limited to,alphanumeric writing on the sputtered or finished disk. An example ofthe disk marking process is the markings used for distinguishing a goodand a defective side of a single-sided finished disk.

[0057] Referencing FIG. 5, in order to identify the defective side 50 ofa one sided finished glass or glass ceramic substrate based magneticdisk 51, a textured ring 52 or other arbitrary pattern is produced onthe defective side of the finished glass disk. Such a marked, finishedglass disk can be used in a load/unload drive and not necessarily in acontact start/stop drive. The ring-marking of a finished glass substratedisk by the application of available Nd:Vanadate laser, or othernear-IR-wavelength lasers, texturing systems can be produced by theforegoing process.

[0058] Currently, one common practice is to mark a one sided disk with apen. With the trend towards increasing volume of one-sided disks thereis a need for a more consistent, lower cost, non-contaminant, andmachine-readable marking system as is provided. The Nd:Vanadate-laserbased texturing systems can be used to make patterns of rings, ridgesand bumps near the inner diameter.

[0059] Additionally, bar-codes and even alphanumeric characters could bewritten on the finished glass substrate magnetic disk surface, with theuse of galvonometer systems, for identifying the production site for thedisk.

[0060] Referring to FIG. 6, in a further embodiment of the presentinvention, a reference disk 60 is produced to calibrate flight height ofa transducer head 62 over a magnetic disk. The reference disk 60contains a protrusion or a pattern of protrusions 64 which substantiallysimulate asperities typically formed on the surface of magnetic disk.Preferably, a plurality of radially spaced circumferential rows ofprotrusions are produced. The protrusions can be spaced apart eitherrandomly or substantially uniformly in the radial direction andcircumferential directions.

[0061] In a preferred embodiment of the invention, the laser light beamfrom a Nd:Vanadate laser is focused on a finished glass or glass/ceramicsubstrate based magnetic disk to obtain the array of protrusions.Preferably, the height of the protrusions is between 12 and 29nanometers for use in calibrating the flight height. The process forcalibrating transducer heads using such a reference is well known in theart.

[0062] Glide height calibration bumps made by a Nd:Vanadate lasertexturing tool on a finished disk is superior to corresponding bumpsmade by a CO₂ laser on a glass substrate. The Nd:Vanadate laser providesa more consistent bump height and shape because the Vanadate laserprovides total surface absorption rather than bulk absorption asprovided by a CO₂ based laser. Furthermore, the Vanadate tool can beused for smaller bump diameter ranges with less focus sensitivity than aCO₂ laser based tool. Also, vanadate laser based tools are a preferableapproach for producing glide height test disks since the existingvanadate laser based tools can be utilized.

[0063] In a further embodiment of the invention, an improved design fora laser texture tool is shown in FIG. 2 and FIG. 7. The illustratedcylindrical lens system 70 converts a circular beam 72 into anelliptically shaped laser beam 74 prior to subjecting the beam to afocusing lens 37 which directs the beam onto the desired location of thedisk surface 30.

[0064] It is advantageous to be able to adjust the shape and orientationof the laser produced bumps in order to gain a tribological improvementin a CSS drive. It is also advantageous to adjust and optimize thecontact area between the head and a bump (protrusion) in a glide heightcalibration test system. The greater the contact area, the greater theimpulse impact (signal generation) between the head and bump during thetesting procedure.

[0065] The cylindrical lens assembly 70 (a Keplerian cylindricaltelescope) provides a system for adjusting the size and aspect ratio ofthe elliptical beam 74. The size and aspect ratio of the elliptical beamcan be adjusted by altering the distance between the two cylindricallenses 76 and 80. In the preferred embodiment a Keplerian cylindricaltelescope is shown. However, it is understood by those skilled in theart that a Galilean cylindrical telescope would also provide the samecapabilities for re-sizing and adjusting the laser beam. The cylindricallens system as shown is simple to assemble and provides for easyadjustment of the size and aspect ratio of the elliptical beam.

[0066] The bump axes with respect to the disk radial direction can beeasily adjusted. Preferably, a cylindrical rotator (not shown) isinstalled with scale markings (in degrees) to rotate the telescope andthus the axes of the elliptical laser beam. Using round shapedcylindrical lenses and simultaneously rotating both lens axes providesthe same advantage as the cylindrical rotator. Thus the aspect ratio andbump axes direction can be adjusted for optimized contact start stopoperation. Preferably this optical assembly can be employed in anexisting laser texturing tool before the final focusing lens in order toadjust the shape of the laser beam entering the focusing lens, andtherefore, the shape of the focused spot size on the disk.

[0067] The circular laser beam 72 enters the first cylindrical lens 76which elongates the beam. At the focal point 78 for the firstcylindrical lens, the beam is elongated. That is, focussed in onedirection. The beam then passes a second cylindrical lens 80. The beamexits the second cylindrical lens as an elliptically shaped laser beam74. The exit beam 74 is focused in a tight elliptical spot with anadjustable aspect ratio.

[0068] In general, the aspect ratio and the size of the exit beam isdetermined by the focusing power of the two lenses and by the spacing ofthe lenses. The direction of the elliptical axis can be adjusted byrotation of the lenses. In the preferred embodiment, the first andsecond cylindrical lenses have the dimensions required to accommodate abeam diameter of 1 to 6 millimeters.

[0069]FIG. 8 illustrates the resulting elongated bumps on the surface ofthe finished glass disk. The area shown is 163 micrometers by 123micrometers.

[0070]FIG. 9 illustrates a three dimensional view of the central portionof an elongated bump of FIG. 8. The illustrated bump height isapproximately 14 nanometers. The length of the mainly flat centralportion of the bump is approximately 22 micrometers.

[0071]FIG. 10 illustrates the profile of the elongated bump along theshort axis A of FIG. 9. FIG. 11 illustrates the profile of the elongatedbump along the central portion of the long axis B of FIG. 9. FIGS. 10and 11 provide a cross sectional illustration of the bump shape as seenin axis A of FIG. 9. The bump profile along the short axis A could bedome shaped, semi-dome shaped, or sombrero shaped. The various shapeshave advantageous applications for CSS disks and glide heightcalibration testing.

[0072]FIG. 12 illustrates a graph of bump height variation versus laserpower for elongated bumps. The bump heights range from 8 nanometers to18 nanometers using a range of laser power between 550 and 670 arbitraryunits.

[0073] While elliptical shaped bumps may also be produced by using otheroptical components, this system and method is an efficient and versatileway of producing the elliptical bumps.

[0074] The invention has been described with particularity as topreferred embodiments. Those skilled in the art will know thatvariations are possible that do not depart from the spirit and scope ofthe invention. Accordingly the invention is limited only by thefollowing claims.

We claim:
 1. A magnetic disk comprising: a glass or glass-ceramic substrate; at least one under layer of a metal alloy applied over the substrate; a magnetic layer applied over said seed layer; a carbon layer applied over said magnetic layer; and at least one bump formed by applying a beam from a near IR laser to the surface of the carbon layer.
 2. The magnetic disk of claim 1 wherein a plurality of bumps form an annular area for a contact start/stop zone.
 3. The magnetic disk of claim 1 wherein the at least one bump is used as part of a glide height calibration process.
 4. The magnetic disk of claim 1 wherein the magnetic disk has a first side and a second side and wherein a plurality of bumps form an annular ring on a side of the disk to mark the side as not being used.
 5. The magnetic disk of claim 1 wherein the at least one bump is part of a disk identifier.
 6. The magnetic disk of claim 1 wherein the at least one bump is an elongated bump formed by passing the laser beam through a cylindrical lens system and wherein the bump shape and aspect ratio of the elongated bump are adjusted by adjusting the cylindrical lens system.
 7. The magnetic disk of claim 1 further comprising a lubrication layer applied over the carbon layer.
 8. The magnetic disk of claim 1 wherein a plurality of under layers are applied to the substrate comprising: a layer of NiAl; a layer of CrV; and a layer of CoCr, and wherein the magnetic layer comprises CoCrPtBo.
 9. The magnetic disk of claim 1 wherein the at least one bump has a height between 10 and 25 nanometers.
 10. The magnetic disk of claim 1 wherein the laser beam is produced by an Nd:Vanadate laser.
 11. A method of manufacturing a magnetic disk comprising the steps of: a) sputtering at least one under layer of a metal alloy over a glass or glass ceramic substrate disk; b) sputtering as a magnetic layer over said under layer; c) sputtering a hard carbon coating over said magnetic layer; and d) applying a beam from a near IR wavelength laser to the surface of the carbon layer to form at least one bump.
 12. The method of claim 11 wherein a plurality of bumps form an annular area for a contact start/stop zone.
 13. The method of claim 11 wherein the at least one bump is used as part of a glide height calibration process.
 14. The method of claim 11 wherein a plurality of bumps form an annular ring to mark a side of the disk for not being used.
 15. The method of claim 11 wherein the at least one bump is part of a disk identifier.
 16. The method of claim 11 wherein the at least one bump is an elongated bump formed by passing the laser beam through a cylindrical lens system and wherein the bump shape and aspect ratio of the elongated bump are adjusted by adjusting the cylindrical lens system.
 17. The method of claim 11 wherein the near IR wavelength laser is an Nd:Vanadate laser.
 18. A magnetic disk comprising: a glass or glass-ceramic substrate; at least one under layer of a metal alloy applied over the substrate; a magnetic layer applied over said seed layer; a carbon layer applied over said magnetic layer; and at least one elongated bump formed by applying a laser beam, from a near IR laser, passed through a cylindrical lens system, to the surface of the carbon layer, wherein the aspect ratio and shape of the bump are adjusted by adjusting the cylindrical lens system.
 19. The magnetic disk of claim 18 wherein the at least one bump is used as part of a glide height calibration process.
 20. The magnetic disk of claim 18 wherein a plurality of bumps form an annular area for a contact start/stop zone. 